Terrestrial LiDAR Survey Techniques

Terrestrial Light Detection and Ranging (LiDAR) is a land-based laser scanner which, combined with a highly accurate differential GPS, enables us to produce 3D computer models of landslides at the coast (The LiDAR).

Digital scanning

BGS Landslides Team using terrestrial LiDAR

Using several scans made at different times, we can accurately calculate volume change and cliff top recession rates. We can also get far more information about how the cliff or landslide is changing than is possible from traditional levelling or photographic techniques.

To make a survey, the team sets up the equipment on the beach in front of the eroding cliff line, or from another vantage point (depending on weather and tidal conditions), and scans a swathe of cliff up to 800 m in width. Scans typically take up to 20 minutes, collecting 2000 individual measurements of the cliff face per minute from a distance of 100–150 m. The data collected in the field by laser scanning and GPS are entered into a modelling package.

Survey sites around Great Britain

As part of a programme of work monitoring coastal erosion and landsliding we are surveying several sites around the coast of Great Britain (see map).

The sites were originally selected to represent mostly unprotected cliffs with 'soft' geology so change could feasibly be measured within the timescales of the project. The sites also have a range of landslide types and sizes.

Some of the 12 sites have been monitored only for a short period before being discontinued or postponed due to inactivity or funding restrictions, but about half of them are being actively surveyed.